Control circuit for a starter solenoid on a vehicle

ABSTRACT

A control circuit for a vehicle starter solenoid which operates so that a second attempt to start an engine cannot be made until a predetermined time has elapsed after a first attempt to start the engine. A starter switch energizes a first rely which completes a circuit to the starter solenoid, completes a selfhold circuit to itself and charges a capacitor connected across the base emitter path of a transistor. The transistor then energizes a second relay which opens a contact between the starter switch and the first relay to break the circuit to the first relay other than through the self-hold circuit. The first relay is then deenergized when the starter switch is opened so that the capacitor discharges through the base-emitter path of the transistor to keep the second relay energized for a predetermined period of time during which the second relay prevents the first relay from being reenergized.

United (72] Inventor Filed Patented Priority Appl No.

States atet William David Hull 7 Thirlmere Avenue. Colne. Iianeashire.

England 28.316

Apr. 14. 1970 July 20,1971 May 27. 1969 Great Britain 26,638

CONTROL CIRCUIT FOR A STARTER SOLENOID 3,452,210 1/1969 (irayetal.

ABSTRACT: A control circuit for a vehicle starter solenoid whichoperates so that a' second attempt to start an engine cannot be madeuntil a predetermined time has elapsed after a first attempt to startthe engine. A starter switch energizes a first rely which completes acircuit to the starter solenoid, completes a self-hold circuit to itselfand charges a capacitor connected across the base emitter path of atransistor. The transistor then energizes a second relay which opens acontact between the starter switch and the first relay to break thecircuit to the first relay other than through the self-hold circuit. Thefirst relay is then deene'rgized when the starter switch is opened sothat the capacitor discharges through the baseemitter path of thetransistor to keep the second relay energized for a predetermined periodof time during which the second relay prevents the first relay frombeing reenergized.

PATENTEU JULPO I97! AT NE S CONTROL CIRCUIT FOR A STARTER SOLENOID ON AVEHICLE This invention relates to a control circuit for a startersolenoid on a vehicle, and has for its object to provide such a circuitin a form in which a second attempt to start the engine cannot be madeuntil a predetermined time has elapsed after a first attempt to startthe engine.

A control circuit according to the invention includes a starter switch,a'first relay which is energized when the starter switch is closed, thefirst relay when energized serving to complete a circuitto the startersolenoid, complete a self-hold circuit to itself, and charge a capacitorconnected across the base-emitter path ,of a transistor and turn thetransistor on, the

transistor then energizing a second relay which opens a contact betweenthe starter switch and the first relay to break the circuit to the firstrelay other than through the self-hold circuit, the first relay beingdeenergized when the starter switch is opened and the capacitor thendischarging through the base-emitter path of the transistor to keep thesecond relay energized for a predetermined period of time during whichthe second relay prevents the first relay from being reenergized even ifthe starter switch is closed.

The accompanying drawing is a circuit diagram illustrating one exampleof the invention.

Referring to the drawing, a road vehicle includes a battery 11 havingits negative terminal earthed and its positive terminal connected to themovable contact 12 of an ignition switch. The contact 12 is movable fromthe off position shown to a first position in which it completes acircuit to a contact 13 providing power to the ignition control circuitsof the vehicle, or the auxiliary loads in the case of a diesel-enginedvehicle, the contact further being movable to a second operativeposition in which it completes a circuit to the contact 13 and a contact14. The contact 14 is connected to one end of the starter solenoid 17 ofthe vehicle through a normally open contact 16a of a first relay havinga coil 16, the other end of the solenoid 17 being earthed, and thesolenoid 17 when energized serving to operate the starter motor of thevehicle. The junction of the contact 1611 and solenoid 17 is connectedto the anodes of a pair of diodes 18, 19 the cathode of the diode 18being earthed through the winding 16, and further connected to thecontact 14 through the normally closed contact 15a of a second relayhaving a coil 15. The cathode of the diode 19 is connected to earththrough a capacitor 23, and is further connected through a variableresistor 22 to the base of an NPN transistor 21, the emitter of which isearthed and the collector of which is connected through the winding 15to the contact 12.

When the contact 12 is moved into engagement with the contact 14 tostart the engine, the circuit is completed by way of the contact 15a andthe winding 16 to energize the first relay, so closing the contact 16aand energizing the solenoid l7. Closure of the contact 16a alsocompletes a self-hold circuit to the winding 16, and charges thecapacitor 23 and then turns the transistor 21 on, so that the winding 15is energized to open the contact 15a, the winding 16 then beingenergized solely through the contact 16a and diode 18 When the contact12 is moved out of engagement with the contact 14, the winding 16 isdeenergized and the contact 16a opens to break the circuit to thesolenoid l7. However, at this stage the contact 15a is still open, andthe transistor 21 remains energized 'tor a predetermined period of timeduring which the capacitor 23 discharges through the resistor 22. Duringthis period of time, the contact 15a remains open so that if anotherattempt is made to start the engine, no circuit is completed to thewinding 16.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent is:

1. A control circuit for a starter solenoid on a vehicle, including astarter switch, a first relay which is energized when the starter switchis closed, the first relay when energized servmg to completea circuit tothe starter solenoid, completes a self-hold circuit to itself, andcharge a capacitor connected across the base-emitter path of atransistor and turn the transistor on, the transistor then energizing asecond relay which opens a contact between the starter switch and thefirst relay to break the circuit to the first relay other than throughthe self-hold circuit, the first relay being deenergized when thestarter switch is opened and the capacitor then discharging through thebase-emitter path of the transistor to keep the second relay energizedfor a predetermined period of time during which the second relayprevents the first relay from being reencrgized even if the starterswitch is closed.

1. A control circuit for a starter solenoid on a vehicle, including astarter switch, a first relay which is energized when the starter switchis closed, the first relay when energized serving to complete a circuitto the starter solenoid, completes a self-hold circuit to itself, andcharge a capacitor connected across the base-emitter path of atransistor and turn the transistor on, the transistor then energizing asecond relay which opens a contact between the starter switch and thefirst relay to break the circuit to the first relay other than throughthe self-hold circuit, the first relay being deenergized when thestarter switch is opened and the capacitor then discharging through thebase-emitter path of the transistor to keep the second relay energizedfor a predetermined period of time during which the second relayprevents the first relay from being reenergized even if the starterswitch is closed.